<template>
  <div class="pagination">
    <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo - 1)">上一页</button>
    <button v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
    <button v-if="startNumAndEndNum.start > 2">···</button>

    <!-- 中间部分 ，v-for遍历--//如果end是10，，就是遍历10次，1~10-->
    <button v-for="(page,index) in startNumAndEndNum.end" :key="index" v-if="page >= startNumAndEndNum.start" @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{page}}</button>


    <button v-if="startNumAndEndNum.end < totalPage-1">···</button>
    <button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo',totalPage)" :class="{active:pageNo==totalPage}">{{totalPage}}</button>
    <!-- 当前页 ==  总页数，不能点击了。 -->
    <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo + 1)">下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
     <!-- <h1>{{startNumAndEndNum}}---{{pageNo}}---{{total}}</h1> -->
  </div>

</template>

<script>
export default {
  name: "Pagination",
  props:['pageNo','pageSize','total','continues'],
  //计算属性，，
  computed:{
    //总共多少页
    totalPage(){
        return  Math.ceil(this.total/this.pageSize)//向上取整
    },
    //计算出--连续的页码-起始数字-结束数字---[连续页码数最少是5]
    startNumAndEndNum(){
        const {continues,pageNo,totalPage} = this//此处的意思就是，把组件身上的这三个属性拿出来。
        //先定义两个变量，存储起始数字和结束数字
        let start = 0,end = 0
        //不正常想象，，总页数没有连续页码（5）数多
        if(continues > totalPage){
            start = 1
            end = totalPage
        }else{
            //正常现象。。总页数 > 连续页码数（5）
            start = pageNo - parseInt(continues/2)//取整
            //结束数字
            end = pageNo + parseInt(continues/2)
            //把不正常的现象的【start数字出现0 | 负数】纠正
            if(start < 1){
                start = 1
                end = continues
            }
            //把出现不正常的现象【end数字大于总页码】纠正
            if(end > totalPage){
                end = totalPage
                start = totalPage - continues + 1  //减去连续页数 + 1
            }
        }
        return {start,end}
    }
  }
};
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
